Method and Device for Machining Elongate Workpieces that are not Rotationally Symmetrical in the Form of Tubine Blades

ABSTRACT

In a method and a device for machining an elongate workpiece that is not rotationally symmetrical in the form of turbine blades, the workpiece is supported by a steady rest that has clamping elements for clamping the workpiece on the cross-section thereof that is not rotationally symmetrical. After clamping the workpiece, the steady rest moves with its open clamping elements along the longitudinal axis of the workpiece into a supporting position. During movement of the steady rest into the supporting position and/or while the supporting position of the steady rest is being changed, a collision between the open clamping elements of the steady rest and the workpiece is prevented by a program-controlled rotation of a rotary part of the steady rest.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT International ApplicationNo. PCT/EP2011/004704, filed Sep. 20, 2011, which claims priority under35 U.S.C. §119 from German Patent Application No. 20 2010 008 628.0,filed Sep. 20, 2010.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a method and a device for machiningelongate, non-rotationally symmetrical workpieces in the form of turbineblades using a steady rest that supports the workpiece in accordancewith the preambles of the first and eighth patent claims.

When elongate workpieces are mechanically machined, they are oftenclamped on the two end faces. Since such a clamping procedure allows theworkpiece to rotate about the longitudinal axis by means of suitableaxes of rotation, the workpiece can be machined on all of thelongitudinal sides without having to rechuck. For specific workpiecegeometries, for example, the milling of turbine blades, such a chuckingoperation is necessary, because the workpiece has to be machinedcontinuously over the entire periphery of the longitudinal sides. In thecase of other workpieces the workpiece can be finish-machined in onlyone chucking operation (in contrast to the clamping on a longitudinalside). As a result, time is saved and accuracy is gained, because errorsarising between multiple chucking operations are avoided.

With such long and relatively fragile components, such as turbineblades, there is often the problem that such workpieces exhibit a verylow rigidity that is much less than the rigidity of the machine that isused. On the one hand such components yield, due to the force of gravityand the machining forces, a feature that results in geometric deviationsof the workpieces; and, on the other hand, a high rigidity is necessaryfor a stable cut in the mechanical machining operation. It is known tosupport the rotationally symmetrical workpieces with a steady rest forthe turning operation. This arrangement dramatically reduces theflexibility of the workpieces.

For example, U.S. Pat. No. 4,177,701 A and DE 10 2007 029 492 B3describe such steady rests for the turning operation of rotationallysymmetrical workpieces. These steady rests have two jaws that can bepivoted in relation to each other and that are configured for receivingthe rotationally symmetrical workpiece. The steady rests have rollerbearings on their inside diameters; and the work pieces are mounted andsupported in a rotational manner by these roller bearings. These steadyrests do not lend themselves to machining elongate workpieces with threedimensional free form surfaces, as is the case, for example, withturbine blades.

DE 360222A describes a machine tool for machining elongate turbineblades. In this case the workpiece is clamped on one end; and thecentral part of the workpiece is held by a rotary part of a steady rest.The steady rest and the rotating spindles are arranged in such a waythat they can be rotated vertically. At the same time the steady restcannot be directed in the direction of the workpiece and is secured onthe vertical axis. The steady rest can be moved vertically by means of ascrew spindle. An automatic control unit makes it possible to lock andunlock the workpiece in the steady rest. The rotary part of the steadyrest is provided with sliding fingers in order to hold the workpiece;and these sliding fingers can be moved in a resilient manner against theworkpiece and can be blocked by means of a device. In this case fivefollow rests are provided for the simultaneous machining of 5workpieces; and these five follow rests can be moved vertically betweena bottom fixed support bracket and an upper support bracket on a countercolumn by means of a slide for the purpose of clamping the workpiece onthe end side. The five turbine blades are inserted transversely throughthe steady rests, which were unlocked beforehand and moved to the oneend of their runway; and these five turbine blades are clamped betweenthe two support brackets. The milling heads that are inserted into therotating spindles begin the machining at the upper end of the blades;and at the same time the slide with the steady rest is also brought tothe suitable height, so that the steady rests can hold the workpieces inthe immediate vicinity of the working range of the tool; and theworkpieces are clamped into the steady rests by means of four fingers.The machining begins, while the milling heads, mounted on the rotatingspindles, engage with the workpieces at their upper end and experience adescending feed motion. The rotary parts of the steady rests areentrained in rotation by means of the blades. Hence, there is noseparate rotary drive of the steady rests. For a defined period of timethe steady rests stay on the same plane; and the slide, which carriesthem, is blocked on this plane. In order to prevent the milling headsfrom moving too far from the region of the steady rests, after they havedescended, the steady rests descend by a predefined step. To this end,the machining operation and the rotating motion of the blades stop; thesteady rests are unlocked; the slide carrying the steady rests isreleased; the slide descends by one step; there is an additionalblocking; the steady rests are clamped anew on the workpieces; and themachining operation and the rotating motion of the blades resume. Theresult of this arrangement is that a continuous and, hence, effectivemachining of the workpieces in not possible. Furthermore, the entiresetup for supporting the workpiece(s) is distinguished by a complicateddesign configuration.

A clamping device for the peripheral-sided clamping of workpieces havingan arbitrary circumferential contour is proposed in DE 195 39 488 A1. Inthis case there are two mutually opposite profiled clamping jaws, whichare disposed on a base body and exhibit clamping surfaces. Each of theseclamping surfaces is formed by a plurality of rams, which can be fluidlymoved independently of each other against the workpiece to be clampedand can be locked in the clamping position. The base body is mounted ina holding device by means of bearing rollers in such a way that the basebody can be rotated about a vertical axis that is directed towards theclamping device. The base body is driven via a gear rim, which isdisposed on the periphery of the base body, and via corresponding drivewheels by means of a drive motor. Both the base body and the holdingdevice have outwards extending recesses in order to insert theworkpiece, thus increasing the risk that high forces will cause theworkpiece to spring back. The workpiece is clamped by means of twoslides that are arranged opposite each other and can be moved inrelation to each other. These slides are provided with profiled clampingjaws in the direction of the workpiece. Each profiled clamping jaw has aplurality of hydraulically adjustable rams, which can be adjusted withrespect to the workpiece in order to clamp the workpiece. In order tomake, for example, a turbine blade, the first step is to finish-machinea holding end in a machining center on a corresponding blank. Then theblank is chucked at this holding end; and the curved blade surfaces areproduced in one or more machining operations in the customary way. Sincethe opposite holding end that still has to be machined is locatedrelatively far away from the chucked holding end, its machining wouldpresent a problem without additional measures. Therefore, the holdingdevice is then moved in the longitudinal direction until it ispositioned next to the machined blade surfaces to be machined. To thisend there are longitudinal guides. At this point the holding device ismoved transversely to the longitudinal direction of the partiallymachined turbine blade on the transverse guides, as a result of whichthis partially machined turbine blade moves through the recess as far asup to the chucking opening. This transverse movement necessitates alarger amount of working space. At this point the holding device ispositioned in such a way that the longitudinal axis of the partiallymachined turbine blade coincides with the axis of rotation of the basebody. At this point the turbine blade is clamped in the base body withthe aid of the profiled clamping jaws. Now the still uncut holding endof the turbine blade can be machined. To this end the partially machinedturbine blade can be rotated in the required way by means of the drivemotor. In this case this rotation can also be accomplished by means ofthe chucked, already machined holding end of the turbine blade. Afterthe machining operation, the profiled clamping jaws are released, andthe holding device is moved laterally away from the turbine blade. Atthis point the next turbine blade can be chucked; and the describedprocedure can be repeated. Since the machining operation has to beinterrupted in order to support by means of the steady rests, thisfeature also constitutes a drawback for the profitability of themachining operation.

Moreover, numerous solutions for clamping workpieces in the form ofturbine blades are known from the prior art (DE 10 2004 056 142 A1, DE10 2005 001 555 A1, DE 100 26 829 C2). These prior art solutionscomprise a plurality of clamping elements, which can be clamped againstthe workpiece surface, but do not allow them a rotational motion of theworkpiece.

The publication DE 28 46 851 A1 also discloses a machine tool formachining turbine blades, wherein the workpiece is supported by a rotarypart of a steady rest. The aim of this solution is to automate thedisplacement processes, the unlocking and the locking of the steady reston its support and on the workpiece. In this case the steady rest isalways supposed to be in the working range of the tool, in order to ruleout as far as possible the generation of vibrations. In this case theworkpiece can rotate in a fixed part of the steady rest. At the sametime the machine has devices for automatically controlling the lockingand unlocking of the workpiece in the rotary part of the steady rest.And the displacement of the steady rest is controlled. Thus, the steadyrest is not actively driven in a rotatable manner, but rather the rotaryparts of the steady rests are entrained in rotation by the blades. As aresult, torsions in the workpiece may occur; and these torsions in turnmay lead to undesired variations in the tolerances.

Furthermore, the steady rest does not move over the clamping point inorder to insert the workpiece.

DE 100 26 829 A1 describes a device for securely clamping a workpiecehaving uneven surfaces. In this case a clamping element or an element,which is coupled in a drive relationship with the clamping element, isprovided with a thread, thereby assigning to the linear feed movement ofthe clamping element a rotating motion of the respective threadedelement in relation to the clamp block; with a rotation actuator, whichis coupled to the rotatable threaded element for its rotary drive; andwith engagable and disengagable means, which can be assigned to at leastone clamping element in order to stop the rotatable threaded element byjamming and/or friction, said means comprising a preferably elasticfriction element, in particular a jamming element, which allows atorque-free stopping of the rotatable threaded element. In this case,too, there is no rotary drive of the clamping element.

A steady rest for machining rotary parts or crankshafts is described inthe publication DE 10 2009 009 056 A1. The workpiece, which isrotationally symmetrical at the clamping point, is supported by thesteady rest in order to compensate for the workpiece deflection; andthis steady rest can be moved along the machining axis in order tochange the workpiece over a clamping point. The steady rest is movedalong the machining axis by means of a control unit. During themachining of a crankshaft, the steady rest rotates passively along. Theentire process of positioning the steady rest, of clamping and centeringthe workpiece runs automatically and is controlled by a control unit. Itis indicated, as a matter of fact, that the steady rest can be used witha suitable drive as a center drive, but only for rotationallysymmetrical workpieces or more specifically crankshafts; and there is nopointer to a specific embodiment. In any event this solution does notlend itself to machining non-rotationally symmetrical workpieces in theform of turbine blades, which have a non-rotationally symmetrical crosssection at the clamping point of the steady rest.

The object of the present invention is to develop a method and a devicefor machining elongate non-rotationally symmetrical workpieces in theform of turbine blades, wherein the workpiece is supported by means of asteady rest, and wherein a simple design configuration of the device aswell as an improved machining cycle are guaranteed.

This engineering object is achieved by means of the features disclosedin the first and eighth patent claims.

Advantageous embodiments will be apparent from the dependent claims.

The method for machining elongate, non-rotationally symmetricalworkpieces in the form of turbine blades is carried out with the use ofa first clamping point for a first end of the workpiece and a secondclamping point for a second end of the workpiece, wherein the workpieceis supported by means of a steady rest, which has clamping elements forclamping the workpiece on its non-rotationally symmetrical crosssection, wherein, according to the invention,

-   -   after clamping the workpiece between the first and the second        clamping point, the steady rest moves with its open clamping        elements along the longitudinal axis of the workpiece into a        supporting position; and    -   during the movement of the steady rest into the supporting        position and/or in the course of changing the supporting        position of the steady rest, a collision between the open        clamping elements of the steady rest and the workpiece is        prevented by means of a program-controlled rotation of a rotary        part of the steady rest.

For loading and unloading the workpiece, the steady rest moves at leastpartially over the first or second clamping point in such a way that theregion between the first and the second clamping point is accessible forinserting and clamping the workpiece. As a result, it is possible tomove the steady rest only longitudinally to the workpiece and todispense with a time-consuming and complicated transverse guide that iscost intensive and requires a larger amount of installation space.Furthermore, the solution according to the invention simplifies theprocess flow.

After clamping the workpiece between the first and the second clampingpoint, the steady rest moves along the longitudinal axis of theworkpiece into a supporting position. At the same time during themovement of the steady rest, collisions with the workpiece are preventedin an advantageous way by means of a program-controlled rotation of thesteady rest.

When the steady rest is in the supporting position, said steady restclamps the workpiece by means of one or more clamping elements,whereupon the machining of the workpiece begins.

Preferably the clamping elements of the steady rest are designed in theform of hydraulic clamping elements. In order to actuate said clampingelements, the steady rest is rotated into a docking position, in which aconnection to the corresponding hydraulic elements can be made and canbe separated. In this docking position the clamping elements are loadedwith a hydraulic pressure by means of the hydraulic elements; and, as aresult, the clamping elements are actuated and transferred into aclamping position, so that the workpiece is chucked and clamped in thesteady rest. At the same time a collision between the open clampingelements of the steady rest and the workpiece is prevented by means ofthe program-controlled rotation of the steady rest.

Then the connection to the hydraulic elements is released and theclamping is still retained; and then the machining of the workpiecebegins.

In order to machine the region of the workpiece that the steady restcovers, the clamping of the clamping elements of the steady rest to theworkpiece is released; and the steady rest is moved along thelongitudinal axis of the workpiece and, if desired, chucked and clampedagain at a different position. In this case, too, there is aprogram-controlled rotation of the steady rest, so that a collision ofthe open clamping elements or other regions of the steady rest with theworkpiece is prevented.

After the clamping elements are chucked and clamped into this positionand, as a result, are fixed, the rotary part of the steady rest can berotated with the workpiece about its longitudinal axis in order toensure machining on the periphery.

It is also possible that the steady rest is arranged between theclamping points during the rotating machining of the workpiece andchucks the workpiece and rotates synchronously to the drives of theclamping points by means of a rotary drive, so that torsional stressesin the workpiece are reduced and prevented.

The device for machining elongate, non-rotationally symmetricalworkpieces in the form of turbine blades, wherein a first clamping pointfor clamping a first end of the workpiece and a second clamping pointfor clamping a second end of the workpiece are provided, and theworkpiece is supported by means of a steady rest, which can be movedalong a longitudinal axis of the workpiece and has clamping elements forclamping the workpiece on its non-rotationally symmetrical crosssection, said clamping elements being arranged on a rotary part and canbe moved between a closed clamping position, with which the workpiececan be clamped, and an open position, in which the workpiece isreleased, wherein, according to the invention, the rotary part has aseparate rotary drive and that the device has a control unit for theprogram-controlled rotation of the rotary part of the steady rest whenthe steady rest is moved along a longitudinal axis of the workpiece,wherein the clamping elements are arranged in the open position duringthe movement of the steady rest.

The steady rest can be moved in an advantageous way along thelongitudinal axis of the first and the second clamping points by meansof a slide and the associated guides. In this case the longitudinal axesof the clamping points are coaxial to each other and to the longitudinalaxis/the machining axis of the workpiece.

Owing to the fact that the workpiece can be moved over the first and/orthe second clamping point, in this position the region between the firstand the second clamping point is accessible for inserting and removingthe workpiece, as a result of which the aforementioned and describedadvantages can be achieved.

To this end the steady rest has a breakthrough, which guarantees athrough-passage of the workpiece as well as the first and/or the secondclamping points.

In order to clamp the workpiece in the region that is located betweenthe end-sided clamping points, the steady rest has one or more clampingelements, which can be moved between a closed clamping position, withwhich the workpiece can be clamped, and an open position, so that aclearance between the clamping elements guarantees the through-passageof the first and/or the second clamping points through the steady rest.

The steady rest has a rotary part, which can be rotated with theworkpiece about its longitudinal axis. The rotary part is mounted in arotatable manner in a base body and has clamping elements for clampingthe workpiece.

The rotary part and the base body are designed in such an advantageousway that both the rotary part and the base body are closed on theperiphery, as a result of which a high rigidity of the steady rest isachieved. This circumferentially closed design is only possible, if thesteady rest does not have to be moved transversely to the workpiece, butrather moved over one of the clamping points in order to insert theworkpiece.

The clamping elements of the steady rest can be connected to or can beseparated from the corresponding hydraulic elements in a dockingposition, so that it is guaranteed that the rotatable part of the steadyrest can be rotated unimpeded in the base body after the separation fromthe hydraulic elements.

The rotary part is provided with a separate rotary drive in anadvantageous way and can be moved along the longitudinal axis of thefirst and the second clamping points by means of a slide and theassociated guides. In this case the longitudinal axes of the clampingpoints are coaxial to each other and to the longitudinal axis/themachining axis of the workpiece.

The invention provides a surprisingly simple possibility for the use ofa steady rest. In this case it is possible to achieve an unimpededinsertion of the workpiece and still retain the distance between theclamping points. Furthermore, the steady rest is not moved transverselyto the workpiece, but rather along the longitudinal axis, so that asimple and compact insertion for machining elongate, non-rotationallysymmetrical workpieces, in particular, turbine blades, is provided.

The invention is explained in detail below by means of one exemplaryembodiment and with reference to the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three dimensional rendering of a device with a steady rest,which is located over a first clamping point for the insertion of aworkpiece.

FIG. 2 is a three dimensional rendering of a device with a steady rest,which is located in a supporting position of the workpiece.

FIG. 3 is a front view of the steady rest with open clamping elements.

FIG. 4 is a sectional view, according to FIG. 3, in the dockingposition.

FIG. 5 is a front view of the steady rest with a turbine blade, clampedby means of the clamping elements, in a machining position.

FIG. 6 is a sectional view according to FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show a three dimensional rendering of a device, wherein,according to FIG. 1, a steady rest 1 is in a position for inserting aworkpiece, which is not illustrated; and, according to FIG. 2, thesteady rest 1 is arranged in a supporting position for machining aworkpiece, which is located in the device and is indicated with thedashed lines.

The device has a bed 2 with a bottom horizontal first leg 2.1 and asecond leg 2.2, which extends vertically upwards away from said firstleg. The bottom leg 2.1 has on its top side a first guide F1. In theupwards extending region 2.2 of the second leg 2.2 a second guide F2comprising two guide rails, which are parallel to each other, isarranged on the vertical side facing the first guide F1. A third guideF3 with two guide rails that are parallel to each other is provided onthe top side of the second leg 2.2.

A first table 3, a second table 4 and a third table 5 with its bottomedge are supported on the first leg 2.1 and are guided by the firstguide F1; and the inner side faces 3 a, 4 a, 5 a of the tables 3, 4, 5that face in the direction of the leg 2.2 are guided by the secondguides F2.

The first table 3 has on its outer side face 3 b a vertically extendingthird guide F5 with two parallel guide rails, through which a firstslide 3.1 is received in such a way that it is vertically adjustable. Afirst clamping point 3.2 for clamping the workpiece, which is not shownin this example, is provided on the first slide 3.1.

The outer side face 4 b of the second table 4 also has verticallyextending fifth guides F5 with two parallel guide rails, through which asecond slide 4.1 is received in such a way that it is verticallyadjustable. The outer side face 4 b of the second slide 4.1 has a sixthguide F6 comprising two guide rails, by which the steady rest 1 isguided in a horizontally moveable manner in the direction of the firstand the second guides F1, F2.

The outer side face 5 b of the third table 5 also has a verticallyextending seventh guide F7 with two parallel guide rails, through whicha third slide 5.1 is received in such a way that it is verticallyadjustable. The second slide 5.1 has in the direction of the firstclamping point 3.2 a second clamping point 5.2 for clamping theworkpiece, which is not shown in this example. The first, the second andthe third table 3, 4, 5 are in essence identical in their construction,so that the second and the third table 4, 5 can be moved relative toeach other and to the first table 3 along the first and the second guideF1, F2. The axis of rotation (machining axis) A of the workpiece, whichis not shown, is coaxial to the axes of the first clamping point 3.2,the second clamping point 5.2 and the steady rest 1.

According to FIG. 1, the second clamping point 5.2 passes through abreakthrough 1.1 of the steady rest 1, so that the region between thefirst clamping point 3.2 and the second clamping point 5.2 is free forinserting a workpiece. To this end the second table 4 with the secondslide 4.1 and the steady rest 1, located thereon, was moved into itsoutermost (in this case the right) end position, so that the steady rest1 reaches over the second clamping point 5.2. In this context the secondclamping point 5.2 is made as thin as possible.

The upper third guide F3 of the bed 1 has a support 6, which can bemoved along the machining axis A. This support carries a milling head 7,with which the machining of the workpiece is carried out.

According to FIG. 2, a workpiece 10 was clamped with a first end 10.1 inthe first clamping point and with a second end 10.2 in the secondclamping point 5.2; and the steady rest 1 was moved out of its endposition, shown in FIG. 1, with the second table 4 (first and secondguides F1, F2) and over the sixth guides F6 on the second slide 4.1 inthe direction of the first clamping point 3.2, so that the steady rest 1is now located in essence in the middle between the first and the secondclamping point 3.2, 5.2 in a supporting position. In this position theworkpiece 10 is clamped in a docking position by means of the clampingelements 15 (see FIG. 5) of the steady rest 1.

The steady rest 1 is actively driven about the axis of rotation A and inthe longitudinal movement. Therefore, at this point a position can bereached automatically for clamping the turbine blade/the workpiece 10.During a movement in the clamped state, the active drive of the rotatingmovement of the steady rest 1 does not generate frictional moments thatcould twist the workpiece 10.

The rotation of the steady rest 1 is carried out by means of a servomotor (not illustrated), which drives a mounted shaft (also notillustrated) by means of a gear train. The modular design of the devicemakes this device easy and economical to manufacture.

In addition to the design variant shown in FIGS. 1 and 2, it is alsopossible to design the first clamping point in such a way that thesteady rest can move in the axial direction over said first clampingpoint in order to load and unload.

FIG. 3 shows a schematic diagram of the steady rest 1 in a front view(in the docking position). The steady rest 1 has an essentiallyrotationally symmetrical rotary part 11 in the form of a ring. Saidrotary part is closed on the peripheral side and is mounted in a basebody 12, which is also closed on the peripheral side, in such a way thatit can be rotated. The rotary part 11 has two clamping plates 13, whichare spaced apart from one another and form a breakthrough 1.1 having aheight H and a width B. These clamping plates lend themselves well toreceiving the workpiece (not illustrated in this example) on theperipheral side. Furthermore, the width B is somewhat larger than thediameter of the second clamping point 5.2 (see FIGS. 1 and 2). Twoclamping jaws 14 are spaced apart from one another on the clampingplates 13 and are provided in pairs that lie opposite one another inthis case on the upper and lower region of the breakthrough 1.1. Thehydraulically actuable clamping elements 15 of these clamping jaws canbe moved towards each other. There are no clamping elements in thecentral region, in order to guarantee that the steady rest 1 with thebreakthrough 1.1 can be moved over the second clamping point 5.2.

A sectional view, according to FIG. 3, is shown in FIG. 4, in additionto the clamping plates in the docking position. It is clear from thissectional view that a connection from the first hydraulic elements 16for actuating the clamping elements 15 in the rotary part 11 to thecorresponding second hydraulic elements 17 in the base body 12 can bemade in the docking position. In this position when the workpiece isinserted, the clamping elements 15 can be actuated in the direction ofthe workpiece by means of the first and the second hydraulic elements16, 17; and then the workpiece is clamped. Then the connection betweenthe first and the second hydraulic elements 16, 17 can be separatedagain; and the clamping is maintained by means of the clamping elements15.

At this point the rotary part 11 of the steady rest 1, as shown in FIG.5, in the base body 12 with the workpiece 10, which is chucked by meansof the clamping elements 15 and which has the form of a turbine blade,can be rotated into the machining position. It is clear from thesectional view shown in FIG. 6 of the steady rest 1 in the machiningposition, which in turn may be found outside the clamping plates, thatthe first hydraulic elements 16 of the rotary part 11 and the secondhydraulic elements 17 of the base body 12 are separated and can bemoved/rotated with respect to each other by the rotation of the rotarypart 11.

FIGS. 4 and 5 show that the rotary part 11 has two opposite diametralexpansions 11.1, by means of which the breakthrough 1.1, which has theheight H, is formed.

It goes without saying that when the rotary part of the steady restrotates, the drives of the first clamping point 3.2 and the secondclamping point 5.2 also rotate in synchronism.

The steady rest 1 allows an automatic clamping of the workpiece 10. Inthis case it is important that this clamping takes place in a forcecontrolled manner. That is, all of the clamping elements 15 pressagainst the workpiece 10 with the same force. As a result, the workpiece10 is not deformed by the clamping cycle. In the solution according tothe invention, this feature is achieved by means of hydraulic cylinders(not illustrated) that are connected in parallel and by means of whichthe clamping elements 15 can be actuated.

The position of the clamping cylinders and the form of the clampingelements 15, mounted on the clamping cylinders, can be adapted to theworkpiece geometry.

After chucking, the clamping elements 15 have to be clamped and, thus,fixed in their clamping position. In the case of a purelyforce-controlled clamping the clamping elements 15 would change theirposition due to the changes in force (machining forces or morespecifically the changes in the direction of the gravitational forcerelative to the workpiece). The clamping is carried out by means of thehydraulically operated clamping sleeves around the hydraulic cylinders(also not illustrated). The clamping force has to be maintained duringthe machining, therefore, during a continuous rotating motion of thesteady rest 1. To this end the hydraulic elements in the form of checkvalves and a concurrently rotating pressure accumulator (notillustrated) are used.

The chucking, clamping and releasing are performed by connecting thesteady rest 1 in a docking position (FIG. 4) between the rotary part 11and the stationary part in the form of the base body 12 of the steadyrest.

The device works in the following way.

For loading and unloading, the steady rest 1 is moved on the side over aclamping point, in this case the first clamping point 5.2. The clampingregion of the workpiece 10 is designed on an end face in such a way thatthe steady rest 1 in the open position of the clamping elements 15 canmove out of an axial “end position” over this position, so that theregion between the first clamping point 3.2 and the second clampingpoint 5.2 remains free for the two end faces of the workpiece 10.

Following the loading of the workpiece 10 and the clamping on its endfaces, the steady rest 1 moves out of the axial end position in theregion of the second clamping point 5.2 per an NC program along thelongitudinal axis/the machining axis A (FIG. 2) over the workpiece asfar as to the desired supporting position and, thus, receives thisworkpiece on the peripheral side. Since the rotation of the steady rest1 is controlled by a numerical control (NC) program, collisions with theworkpiece 10 are prevented.

Then the workpiece 10 and the steady rest 1 are rotated into the dockingposition (FIGS. 3 and 4). The hydraulic pressure is connected; and theworkpiece 10 is chucked and clamped. Following the connection of thehydraulic unit, the steady rest 1 can be rotated with the workpiece 10into the machining position (FIGS. 5 and 6); and the machining begins.In order to be able to machine the region, in which the steady rest 1 isstanding, this steady rest is then released, moved and eventuallychucked and clamped again at a different position.

The solution according to the invention makes it possible, according toone exemplary embodiment that is not illustrated, to move the steadyrest along the longitudinal axis A as the machining operation advances,when the clamping by means of the clamping elements is configuredaccordingly.

In summary, the invention provides an effective method for machiningnon-rotationally symmetrical workpieces. The use of a steady rest thatis closed on the peripheral side prevents the steady rest from bendingdue to the clamping forces of the clamping elements. Only an axial backand forth movement of the steady rest between the loading and removalposition and the machining position is required, as a result of whichless working space is needed; and the design configuration is simplerand more reliable.

1. A method for machining an elongate, non-rotationally symmetricalworkpiece in the form of a turbine blade, wherein a first clamping pointfor a first end of the workpiece and a second clamping point for asecond end of the workpiece are provided, and the workpiece is supportedby a steady rest, which has clamping elements for clamping the workpieceon a non-rotationally symmetrical cross section, comprising: afterclamping the workpiece between the first and the second clamping point,moving the steady rest with its open clamping elements along thelongitudinal axis of the workpiece into a supporting position; andduring movement of the steady rest into the supporting position and/orwhile changing the supporting position of the steady rest, preventing acollision between open clamping elements of the steady rest and theworkpiece by way of a program-controlled rotation of a rotary part ofthe steady rest.
 2. The method as claimed in claim 1, wherein, forloading and unloading the workpiece, the steady rest moves at leastpartially over the first or second clamping point in such a way that theregion between the first and the second clamping points is accessiblefor inserting and clamping the workpiece.
 3. The method as claimed inclaim 1, wherein, in the supporting position, the steady rest clamps theworkpiece with one or more clamping elements, and then the machining ofthe workpiece begins.
 4. The method as claimed in claim 1, wherein, theclamping elements of the steady rest are hydraulic clamping elements,which may be found on a rotary part of the steady rest; and wherein, foractuating the clamping elements, the rotary part of the steady rest isrotated into a docking position, in which a connection to thecorresponding hydraulic elements can be both made and be separated. 5.The method as claimed in claim 1, wherein, in the docking position ahydraulic pressure is coupled to the clamping elements by the hydraulicelements; wherein, as a result, the workpiece is chucked and clamped;wherein, then, the connection to the hydraulic elements is released andthe clamping is retained; wherein, then, the rotary part of the steadyrest can be rotated out of the docking position; and wherein themachining of the workpiece begins.
 6. The method as claimed in claim 1,wherein, in order to machine the region of the workpieces that thesteady rest covers, clamping of said steady rest to the workpiece beingreleased, the steady rest is moved along the machining axis and, ifdesired, chucked and clamped again at a different position; and whereinthe program-controlled rotation of the steady rest prevents a collisionbetween the open clamping elements of the steady rest and the workpiece.7. The method as claimed in claim 1, wherein, during the rotatingmachining of the workpiece, the steady rest is arranged between theclamping points and chucks the workpiece and rotates synchronously tothe drives of the clamping points by way of a rotary drive, so thattorsional stresses in the workpiece are reduced or prevented.
 8. Adevice for machining an elongate, non-rotationally symmetrical workpiecein the form of a turbine blade, comprising: a first clamping point forclamping a first end of the workpiece, a second clamping point forclamping a second end of the workpiece are provided, and a steady restby which the workpiece is supported, which can be moved along alongitudinal axis of the workpiece, and which has clamping elements forclamping the workpiece on its non-rotationally symmetrical crosssection, wherein the clamping elements are arranged on a rotary part andcan be moved between a closed clamping position, in which the workpiececan be clamped, and an open position, in which the workpiece isreleased, wherein the rotary part has a separate rotary drive, whereinthe device has a control unit for program-controlled rotation of therotary part of the steady rest when the steady rest is moved along alongitudinal axis of the workpiece, and wherein the clamping elementsare arranged in open positions during movement of the steady rest. 9.The device as claimed in claim 8, wherein the steady rest can be movedalong a longitudinal axes of the first and the second clamping points byway of a slide and associated guides, and wherein the longitudinal axesof the clamping points are coaxial to each other and to the longitudinalaxis of the workpiece.
 10. The device as claimed in claim 8, wherein thesteady rest can be moved over the first clamping point and/or the secondclamping point, and in this position the region between the firstclamping point and the second clamping point is accessible for insertingand removing the workpiece.
 11. The device as claimed in claim 10,wherein the steady rest has a breakthrough, which guarantees athrough-passage of the workpiece and the first clamping point and/or thesecond clamping point.
 12. The device as claimed in claim 10, whereinthe steady rest has clamping elements, which can be moved between aclosed clamping position, with which the workpiece can be clamped, andan open position; and wherein a clearance between the clamping elementsguarantees the through-passage of the first clamping point and/or thesecond clamping point.
 13. The device as claimed in claim 8, wherein therotary part is mounted in a rotatable manner in a base body.
 14. Thedevice as claimed in claim 13, wherein the rotary part and the base bodyare closed on the peripheral side.
 15. The device as claimed in claim 8,wherein the clamping elements of the steady rest can be connected to orseparated from the corresponding hydraulic elements in a dockingposition; and wherein the rotary part cannot be rotated until after theseparating the clamping elements from the corresponding hydraulicelements.